Building upon exciting new discoveries that link genes encoding presenilin 1 (PS1) (chromosome 14) and PS2 (chromosome 1) to cases of familial Alzheimer's disease (FAD), this Program Project proposal takes advantage of established expertise and complementary strengths of scientists at John Hopkins who are committed to in vitro and in vivo investigations of inherited neurogenerative diseases. The first project outlines research to examine properties of PS1/PS2, including studies with newly generated probes and antibodies to examine the expression of PS in cell culture paradigms and distribution in tissues and brain regions of developing/adult rodents, monkeys, and humans. In transfected cells and cultured neurons from transgenic mice, we will define the topology and biology of PS and the ways in which mutations influence the biology of PS, amyloid precursor protein (APP) trafficking/processing, and the production of the beta- amyloid protein (A beta). The second project we will use a recently developed expression plasmid to create transgenic mice that express high levels of wild-type and mutant PS1/PS2. Behavioral and brain abnormalities will be characterized using approaches that have been successful in studies of humans and animal models. The influences of wild-type or mutant PS1 on PS2 on APP transgenes. We believe that theses studies will produce for the first time, PS mutation-linked trangenic models of FAD in which it will be possible to examine the mechanisms of disease and to test potential therapies. The third project is designed to clarify the in vivo function of PS using gene targeting strategies to ablate PS genes and to examine the phenotypes of PS nulls. To define molecules interacting with PS, we will use the yeast two-hybrid system, a strategy that has proved very successful in several settings including the identification of HAP-1, which interacts with huntington. In concert the projects should clarify some of the most important features of the normal biology of PS and define the mechanisms whereby mutations in these genes cause FAD. Finally, the PS mice, which we intend to make widely available, will be extraordinary valuable models for testing new therapies.